si4713.rst (6888B)
1.. SPDX-License-Identifier: GPL-2.0 2 3.. include:: <isonum.txt> 4 5The Silicon Labs Si4713 FM Radio Transmitter Driver 6=================================================== 7 8Copyright |copy| 2009 Nokia Corporation 9 10Contact: Eduardo Valentin <eduardo.valentin@nokia.com> 11 12 13Information about the Device 14---------------------------- 15 16This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. 17Basically, it has transmission and signal noise level measurement features. 18 19The Si4713 integrates transmit functions for FM broadcast stereo transmission. 20The chip also allows integrated receive power scanning to identify low signal 21power FM channels. 22 23The chip is programmed using commands and responses. There are also several 24properties which can change the behavior of this chip. 25 26Users must comply with local regulations on radio frequency (RF) transmission. 27 28Device driver description 29------------------------- 30 31There are two modules to handle this device. One is a I2C device driver 32and the other is a platform driver. 33 34The I2C device driver exports a v4l2-subdev interface to the kernel. 35All properties can also be accessed by v4l2 extended controls interface, by 36using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). 37 38The platform device driver exports a v4l2 radio device interface to user land. 39So, it uses the I2C device driver as a sub device in order to send the user 40commands to the actual device. Basically it is a wrapper to the I2C device driver. 41 42Applications can use v4l2 radio API to specify frequency of operation, mute state, 43etc. But mostly of its properties will be present in the extended controls. 44 45When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. 46 47Properties description 48---------------------- 49 50The properties can be accessed using v4l2 extended controls. 51Here is an output from v4l2-ctl util: 52 53.. code-block:: none 54 55 / # v4l2-ctl -d /dev/radio0 --all -L 56 Driver Info: 57 Driver name : radio-si4713 58 Card type : Silicon Labs Si4713 Modulator 59 Bus info : 60 Driver version: 0 61 Capabilities : 0x00080800 62 RDS Output 63 Modulator 64 Audio output: 0 (FM Modulator Audio Out) 65 Frequency: 1408000 (88.000000 MHz) 66 Video Standard = 0x00000000 67 Modulator: 68 Name : FM Modulator 69 Capabilities : 62.5 Hz stereo rds 70 Frequency range : 76.0 MHz - 108.0 MHz 71 Subchannel modulation: stereo+rds 72 73 User Controls 74 75 mute (bool) : default=1 value=0 76 77 FM Radio Modulator Controls 78 79 rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider 80 rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 81 rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 82 rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' 83 rds_radio_text (str) : min=0 max=384 step=32 value='' 84 audio_limiter_feature_enabled (bool) : default=1 value=1 85 audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider 86 audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider 87 audio_compression_feature_enabl (bool) : default=1 value=1 88 audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider 89 audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider 90 audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider 91 audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider 92 pilot_tone_feature_enabled (bool) : default=1 value=1 93 pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider 94 pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider 95 pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 96 tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider 97 tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider 98 99Here is a summary of them: 100 101* Pilot is an audible tone sent by the device. 102 103- pilot_frequency - Configures the frequency of the stereo pilot tone. 104- pilot_deviation - Configures pilot tone frequency deviation level. 105- pilot_enabled - Enables or disables the pilot tone feature. 106 107* The si4713 device is capable of applying audio compression to the 108 transmitted signal. 109 110- acomp_enabled - Enables or disables the audio dynamic range control feature. 111- acomp_gain - Sets the gain for audio dynamic range control. 112- acomp_threshold - Sets the threshold level for audio dynamic range control. 113- acomp_attack_time - Sets the attack time for audio dynamic range control. 114- acomp_release_time - Sets the release time for audio dynamic range control. 115 116* Limiter setups audio deviation limiter feature. Once a over deviation occurs, 117 it is possible to adjust the front-end gain of the audio input and always 118 prevent over deviation. 119 120- limiter_enabled - Enables or disables the limiter feature. 121- limiter_deviation - Configures audio frequency deviation level. 122- limiter_release_time - Sets the limiter release time. 123 124* Tuning power 125 126- power_level - Sets the output power level for signal transmission. 127 antenna_capacitor - This selects the value of antenna tuning capacitor 128 manually or automatically if set to zero. 129 130* RDS related 131 132- rds_ps_name - Sets the RDS ps name field for transmission. 133- rds_radio_text - Sets the RDS radio text for transmission. 134- rds_pi - Sets the RDS PI field for transmission. 135- rds_pty - Sets the RDS PTY field for transmission. 136 137* Region related 138 139- preemphasis - sets the preemphasis to be applied for transmission. 140 141RNL 142--- 143 144This device also has an interface to measure received noise level. To do that, you should 145ioctl the device node. Here is an code of example: 146 147.. code-block:: none 148 149 int main (int argc, char *argv[]) 150 { 151 struct si4713_rnl rnl; 152 int fd = open("/dev/radio0", O_RDWR); 153 int rval; 154 155 if (argc < 2) 156 return -EINVAL; 157 158 if (fd < 0) 159 return fd; 160 161 sscanf(argv[1], "%d", &rnl.frequency); 162 163 rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); 164 if (rval < 0) 165 return rval; 166 167 printf("received noise level: %d\n", rnl.rnl); 168 169 close(fd); 170 } 171 172The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under 173include/linux/platform_data/media/si4713.h. 174 175Stereo/Mono and RDS subchannels 176------------------------------- 177 178The device can also be configured using the available sub channels for 179transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. 180Refer to the V4L2 API specification for proper use of this ioctl. 181 182Testing 183------- 184Testing is usually done with v4l2-ctl utility for managing FM tuner cards. 185The tool can be found in v4l-dvb repository under v4l2-apps/util directory. 186 187Example for setting rds ps name: 188 189.. code-block:: none 190 191 # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" 192